The present invention relates to an ink jet recording head comprising a recording element substrate and a driving element which are pressed together, wherein the recording element substrate comprises recording elements for ejecting ink, and the driving element substrate comprises driving elements for driving the recording elements in response to externally inputted image signals.
Regarding the terminology in the present invention, a word xe2x80x9crecordingxe2x80x9d means xe2x80x9cattaching meaningful patterns such as letters or geometrical figures to a recording medium as well as xe2x80x9cattaching meaningless patterns to a recording medium.xe2x80x9d
(A) The present invention is applicable to an apparatus such as a printer which records patterns on a recording medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramics. It is also applicable to an apparatus such as a copying machine, a facsimile machine comprising a communication system, or a word processor comprising a printing section. Further, it is applicable to an industrial recording apparatus integrally comprising a printing section and various processing apparatuses.
FIG. 1(a) is a plan view of the structure of a conventional recording element substrate of an ink jet recording head employed in an ink jet recording apparatus or the like, and FIG. 1(b) is a section of the structure illustrated in FIG. 1(a), at A-A1 line.
Referring to FIGS. 1(a) and 1(b), a reference numeral 1501 designates a substrate on which recording elements are disposed; 1502, a heat generating element, that is, a layer of heat generating resistor, for example, HfB2; 1503, a common electrode composed of aluminum; 1504, an individual electrode composed of aluminum; 1505a and 1505b, patterned Al wiring; 1506, a photosensitive polyimide layer as an anti-oxidation layer as well as an insulative layer; and a reference numeral 1508 designates a Ta layer as an anti-cavitation layer.
The recording element substrate illustrated in FIGS. 1(a) and 1(b) generates thermal energy from the HfB2 layer as electric current is flowed through the HfB2 layer 1510 as a heat generating resistor layer. More specifically, in order to generate thermal energy in the heat generating element 1502, driving current is externally flowed into the HfB2 layer 1502 through the individual electrode 1504 and the patterned wiring 1505a, and is flowed out through the patterned wiring 1505b and the common electrode 1503.
(B) FIG. 2 illustrates the structure of a recording element unit employing the recording element substrate described above. This recording element unit is provided with ink paths 1520 which lead to corresponding ejection orifices 1521. In each ink path 1520, a heating element is disposed. Ink is supplied into a liquid chamber 1530 through an ink supply port (unillustrated) of a top plate 1540, and is delivered to the ink path 1520 from the liquid chamber 1530.
As a driving signal is given to the heating element, a bubble is developed in the ink in the ink path, whereby the ink is ejected from the ejection orifice 1521.
Normally, a plurality of the heat generating elements 1502, which are constituted of a combination of the HfB2 1510, the dedicated electrode 1504, the patterned wiring 1505a, and the patterned wiring 1505b, are disposed on a single recording substrate. Deposing a plurality of heat generating elements on a single recording element substrate makes it possible to realize an ink jet recording apparatus capable of printing a plurality of dots at the same time, increasing recording speed. In particular, in the present situation in which demands for high density and high recording speed are rather high, it is quite common that a plurality of lines are recorded at the same time through a single scanning pass, and also, a recording element unit in which a large number of heat generating elements are disposed in high density is very common.
In order to record a plurality of dots by disposing a plurality of recording elements in a single recording unit, each recording element must be independently controlled (turned on or off). Such control is possible by providing the recording element unit with a means for selectively driving each of the heat generating elements (hereinafter, driving element). However, in the case of a long recording unit, that is, a recording unit comprising a large number of heat generating elements, the driving means is formed on a separate substrate (hereinafter, driving element substrate), and is connected to the recording unit. The reason for rendering the recording element unit and the driving element substrate independent from each other is due to the problem that when the recording element and the driving element are disposed on the same substrate, presence of a defect in either the recording element or the driving element causes the entire unit to stop functioning.
As for the technology (method) for electrically connecting the recording element substrate to the driving element substrate, there is a method disclosed in U.S. Pat. No. 5,243,363.
According to the aforementioned connecting method, a structure substantially the same as the structure illustrated in FIGS. 1(a) and 1(b) is employed. More specifically, a bump-like portion is formed on each of the dedicated electrodes, and, a recording element substrate 7001 attached to the main base board 7005 is joined with the driving element substrate 7002 having a driving IC 7003, by the application of pressure.
Japanese Laid-Open Patent Application No. 302,829/1989 discloses a different method which employs an electrical connecting member. FIGS. 4(a)-4(c) depict the connecting method disclosed the above patent application.
In FIG. 4, a reference numeral 1704 designates a recording element substrate; 1705, a driving element substrate; 1714 and 1715, electrode portions; and reference numerals 1719 and 1720 designate insulative film. Further, a reference numeral 1703 designates an electrically connective member; 1717, an electrically conductive member; and a reference numeral 1718 designates a supportive member for supporting the electrically conductive member 1717. The pitch of the electrically conductive member 1717 is narrower than those of the electrodes 1714 and 1715.
First, the recording element substrate 1704, driving element substrate 1705, and electrically connective member 1703 are arranged as shown in FIG. 4(a), and then, are pressed together as shown in FIG. 4(b). FIG. 4(c) gives the overall appearance of the joined three members. Since the pitch of the electrically conductive member 1717 is smaller than those of the electrodes 1714 and 1715, it is unnecessary to precisely position them; the electrodes 1714 and 1715 can be electrically connected through the electrically conductive member 1717, simply by pressing them together.
FIGS. 5 and 6 illustrate an example of a recording head constituted of a recording element and a separate driving element substrate. FIG. 5 is a perspective view of the recording head, and FIG. 6 is a section thereof, as seen from the direction indicated by an arrow mark in FIG. 5.
In the recording head illustrated in FIGS. 5 and 6, a recording element substrate 8001 and a driving element substrate 8002 are fixed to a main base board 8005 and an auxiliary substrate 8004, respectively. A filter for removing the bubbles and foreign matter within the recording liquid is fixed to the main base board 8005.
As for the method for electrically connecting the recording element substrate 8001 and the driving element substrate 8002, first, the connective electrode of the driving element substrate 8002 is accurately positioned relative to the connective electrode of the recording element substrate 8001, and the, the auxiliary base board 8004 is pressed toward the main base board by the pressing plate 8007, with an elastic member 8008 being interposed between the auxiliary base board and the pressing plate 8007.
Recording liquid is delivered to the recording element unit by an ink delivery system in which the recording element unit is connected to a filtering apparatus 8016 with the use of an ink delivery tube 8013, and the filtering apparatus 8016 and an unillustrated ink container are connected with the use of an ink delivery tube 8013.
When assembling the conventional ink jet recording head described above, or replacing it due to the failure of the recording element substrate 8001 or the recording element unit, the procedure for electrically connecting or disconnecting the recording element substrate and the driving element substrate, and the procedure for connecting or disconnecting the recording element unit and the ink delivery system, must be separately carried out, creating a problem in that it takes too much time and labor, and this problem had to be solved.
Also, even when only the recording element substrate needs to be replaced, the filtering apparatus and the ink delivery tube must be replaced together with the recording element substrate, adding to the time and cost for replacing the recording element substrate. This problem must be also solved.
The present invention was made in view of the above described problems which the conventional method has, and its primary object is to greatly simplify the procedure for replacing the recording element substrate, and also to reduce the component count, so that it becomes possible to provide an inexpensive ink jet recording apparatus which allows the recording element substrate to be quickly replaced.
The structure of the ink recording head in accordance with the present invention made to accomplish the above objects is as follows.
According to the present invention, an ink jet recording apparatus comprises: an ink path leading to an ejection orifice for ejecting ink; a liquid chamber from which ink is delivered to the ink path; a recording element substrate having a plurality of recording elements of generating the ink ejecting energy; a driving element substrate having a plurality of driving elements for selectively driving the recording elements; and a pressing means for providing the pressure for keeping the recording element substrate and the driving element substrate physically in contact with each other, wherein the pressing means comprises an ink delivery system for delivering ink from the liquid chamber to the ink jet head.
An ink jet head cartridge comprises the ink jet recording head described above, and an ink container which holds the ink to be delivered to the ink jet head.
An ink jet recording apparatus comprises the ink jet recording apparatus described above, and a means for generating a signal which drives the ink jet recording head.
Further, according to the present invention, component count, and assembly or disassembly steps, can be greatly reduced by adopting the structure described above.